NEMESIS Bioregion Distribution:

This species is a freshwater species with occurrences in tidal fresh or brackish waters and does not have a marine bioregion map associated with it. Please click on the Distribution Details tab for a North American distribution map. Additional information on this species and its distribution can be found in the USGS Nonindigenous Aquatic Species Database

First Non-native North American Marine/Estuarine Record: 1938
First Non-native West Coast Marine/Estuarine Record: 1938
First Non-native East/Gulf Coast Marine/Estuarine Record: 1960

General Invasion History:

Asian freshwater clams Corbicula spp. are native to Asia, including Indonesia and the Philippines and probably also to Africa and Australia (Counts 1986; McMahon 1983; McMahon 2000). Several hermaphroditic genetic lineages of these clams have been introduced to North America, Europe, South America, and Hawaii (Lee et al. 2005; Hedtke et al. 2008; Pigneur et al. 2011). We will refer to the most widespread form (lineage A of Siripattrawan et al. 2000; lineage R of Pigneur et al. 2011) as C. fluminea, and its origin as 'Asia', although the correct name may be C. leana, from Japan (Hedtke et al. 2008) (see Description). Corbicula fluminea is believed to have been introduced to Western North America from Asia before 1924, and then spread rapidly across the continent (McMahon 1983). The most likely vector was the transport of clams as a potential food item by Asian immigrants (Counts 1986; McMahon 1983). Its spread across North America was rapid, and indicates a wide variety of vectors. Likely modes of transport include use as food or bait; transport on barges, dredges, anchors, and digging machinery; use as an aquarium animal; and ballast water transport of pediveligers. Its spread in relatively unpopulated, undisturbed watersheds in Mexico and South America suggests that this species also has natural modes of spread, including the possibility of transport in bird and fish guts. Corbicula fluminea colonizes slow-moving rivers, lakes, and low-salinity, mostly fresh to oligohaline regions (0-5 PSU) of estuaries (McMahon 1983; McMahon 2000).

N.B. Corbicula lineage B, genetically related to C. fluminea from China, Korea, and Thailand, has been found in Utah and New Mexico (Siripattrawan et al. 2000; Lee et al. 2005), but is not known to occur in US estuaries.

North American Invasion History:

Invasion History on the West Coast:

Corbicula fluminea was first collected (only as dead shells) on the Pacific Coast in the Nanaimo River, on Vancouver Island, British Columbia, in 1924 (Kirkendale and Clare 2008). In 1938, it was found in the Columbia River at Knappton, Washington. It spread across the southern part of the state eastward into the Snake River, and was widespread in the Columbia Basin by 1969-71. It was first collected in the Sacramento River, California in 1945 and soon spread through the Delta region and fresher parts of the estuary via canals. Corbicula fluminea reached lower Colorado-Imperial Valley canals by 1953; Phoenix, Arizona by 1956; and by the 1970's had fouled irrigation systems and reservoirs in most of the lower Colorado Basin (Counts 1986), including the Colorado Delta in Mexico (Mellink and Ferreira-Bartrina 2000). By the 1970-80s, it was found in many smaller drainages of the West Coast, including the Willapa River, Washington (in 1971, Counts 1991); Siuslaw River, Oregon (in 1971, Counts 1991); Coos River, Oregon (Carlton 1989); the Smith River in northern California (Carlton 1979); the Santa Margarita River in Camp Pendleton, California (in 1983, Counts 1991); and the Sweetwater River, flowing into San Diego Bay, in southern California (2005, USGS Nonindigenous Aquatic Species Program 2007). In 2008, established populations have been found in inland lakes on Vancouver Island and isolated collections have been made in the Fraser River Basin, British Columbia (Kirkendale and Clare 2008). Collections of this freshwater clam from several marine sites (e.g. Point Loma, San Diego in 1964; Anaheim Bay in 1961; Santa Barbara Harbor in 1986; Counts 1986) probably represent shells washed into the sea by floods.

Invasion History on the East Coast:

Corbicula fluminea spread rapidly up the Atlantic Coast in the 1970s. It was first collected in Altamaha River, Georgia in 1971, and was abundant by 1974. Many collections to the north were nearly simultaneous: Pee Dee River, Savannah River, and Intracoastal Waterway, South Carolina (in 1972-76); Catawba River, North Carolina (in 1971); James River, Richmond, Virginia (in 1971, probably before 1968); Potomac River, Washington D.C. (in 1976); Susquehanna Flats, Upper Chesapeake Bay (in 1975); Delaware River, New Jersey-Pennsylvania (in 1971). Further north, this clam reached the Raritan River, New Jersey in 1982 (Counts 1986); but has not yet been reported from the Hudson River (Mills et al. 1997). However, in 1990, it colonized the tidal Connecticut River at East Haddam, Connecticut. This population is largely dependent on effluent from a nuclear power plant for winter survival (Balcom 1994; Morgan et al. 2003). The northward range of this clam continues to expand - it is known from several freshwater lakes in Rhode Island and Massachusetts, and from the Charles River in Watertown and Cambridge, Massachusetts (in 2001, 2005, USGS Nonindigenous Aquatic Species Program 2008; in 2003, Museum of Comparative Zoology 2008).

Corbicula's history in the Chesapeake Bay gives an example of its spread through an estuary and watershed. It was first recorded in 1971, in a tidal river near Richmond, but the size distribution indicated some shells were at least 3 years old. By 1972, it was found from River Mile 45-80 (measured from river mouth), and the lower Appomattox River (Diaz 1974). By 1976, it comprised ~ 95% of all bivalves in the river (Diaz 1994). Further downstream, at Hog Island Point, Surry, Virginia (0-5 PSU), it was less abundant, except during periods of low salinities (Jordan and Sutton 1984). By 1984, C. fluminea had spread through almost the entire non-tidal James River system, except for a few highly polluted areas (Clarke 1986). In the Potomac River, the first record of C. fluminea was in 1977 in the tidal reaches of the river. By 1978, it was present from the center of Washington (River Mile 84.5 – 95, at the mouth of Piscataway Creek), and by 1979 it was causing problems in Potomac Electric Company plants in Alexandria (Dresler and Cory 1980). Corbicula fluminea reached a biomass peak in 1984 and declined to about one-eighth of its peak by 1992, but still comprises a substantial biomass and is the dominant mollusc in the tidal reaches of the Potomac (Phelps 1994). A 'large population' occurred at Whites Ferry, Maryland in the nontidal river (~40 km upstream of Washington D.C., 1981) (Kennedy and Huekelem 1985) and the clam now occurs throughout the entire Potomac drainage (Taylor 1985). In the upper Bay, the first record of C. fluminea was in 1977 at Susquehanna Flats, but it probably arrived by 1975, and is now present from Havre de Grace to Turkey Point (Counts 1986). Corbicula fluminea was first collected in the Susquehanna River at Conowingo Dam, in 1980, but was not found above the dam (Counts 1986; Nichols and Domermuth 1981). By 1984, it was found above the dam, and by 2001 C. fluminea had colonized the North Branch of the Susquehanna in Pennsylvania and was present along at least 135 river miles (217 km) of the Susquehanna in PA (Mangan 2002). By 2002, it had colonized the upper reaches of the Susquehanna in Chengango and Otsego counties, New York (2005, USGS Nonindigenous Aquatic Species Program 2008).

In the Great Lakes St. Lawrence Basin, Corbicula fluminea reached Lake Erie in 1978 and Lake Michigan by 1984 (Mills et al. 1993). The Asian Clam is established in Lake Erie, but in Lake Michigan and Lake Superior it is confined to power plant and warm sewage effluents, where they are vulnerable to power plant shutdowns (USGS Nonindigenous Aquatic Species Program 2008; Trebitz et al. 2012). In 2009, C. fluminea was found in the fresh tidal St. Lawrence River, in the thermal plume of a nuclear power plant, downstream of Trois Rivieres, Quebec. This is its northernmost occurrence in eastern North America. Establishment of the clam here is uncertain, but it was found at sites where the influence of the thermal plume was minimal (Simard et al. 2012).

Invasion History on the Gulf Coast:

In the Eastern U.S., C. fluminea was first found in the Ohio River at Paducah, Kentucky in 1957, and rapidly spread through the Mississippi system, and adjacent rivers. To the east, it was dominant in the Tennessee River by 1969, and moved upstream to Cincinnati (1964). To the west, the Arkansas, Black and White Rivers in Arkansas were colonized by 1970; Lake Overholser, Oklahoma was colonized by 1969; and Cherry Creek Reservoir, Arapahoe County, Colorado was colonized by the 1990s (Nelson and McNabb 1994). Corbicula fluminea rapidly moved downstream, reaching Louisiana in the Mississippi by 1962; the Calcasieu River, Louisiana in 1961; the Escambia River in Century, Florida by 1960; and Galveston Bay, Texas by 1967 (Counts 1986). By 2004, it had colonized nearly every coastal county in Texas, and was expected to be found in most tidal fresh tributaries (Karatyev et al. 2005).

Invasion History in Hawaii:

Corbicula fluminea was first collected on Kauai at the Hanalei National Wildlife Refuge, in irrigation canals in 1971 (Counts 1986; USGS Nonindigenous Aquatic Species Program 2008). It was sold as food in markets in Oahu in 1977 (Counts 1986), and found in streams on Maui in 1988 and the island of Hawaii in 1991 (USGS Nonindigenous Aquatic Species Program 2008). In a recent survey of coastal streams, it was found on Maui, Kauai, and Oahu, only in freshwater (MacKenzie and Bruland 2012). The Asian Clam may have been brought to the islands as food by immigrants or as an aquarium animal, and was probably spread further with use as bait, or with irrigated agriculture.

Invasion History elsewhere in the World:

Corbicula fluminea is widespread in central Mexico, including drainages with little human population or disturbance (Lopez-Lopez et al. 2010). It has been introduced to Central America in Panama, including the Panama Canal system (Counts et al. 2004; Lee et al. 2005), possibly with Tilapia fish stock imported from the US for aquaculture (Counts et al. 2004). In the 1970s, it was introduced to the Rio de La Plata in Argentina (both lineages A and C, Lee et al. 2005) and soon colonized the rivers in Rio Grande do Sul, Brazil. In Brazil, it is known from 10 of 26 states (da Silva and Barros 2011). Corbicula fluminea also invaded rivers in Venezuela in the 1980s (McMahon 2000), and is now in Ecuador and Peru (Lee et al. 2005). In 1998, C. fluminea was collected in the Cayey River, Puerto Rico (Williams et al. 2001). It is now found in reservoirs in several watersheds on the island (USGS Nonindigenous Aquatic Species Program 2012).

Corbicula fluminea invaded Europe around 1980, first appearing in the Dodogne River, France or the Tajo/Tagus River in Spain and Portugal (McMahon 1983; Araujo et al. 1993). The probable source was North America, since the most widespread genotype is identical or closely related to the North American 'form A' (Pfenninger et al. 2002; Pigneur et al. 2011). In 1987, Corbicula spp. appeared in the Rhine river and quickly became very abundant in the middle and lower reaches, occurring in the tidal fresh portions of the Delta in the Netherlands by 1990 (den Hartog et al. 1992, Wolff 2005). It has invaded many rivers in Western Europe, and is expanding its range towards the Baltic and Black Sea coasts. In France, Corbicula spp. is found in many of the rivers of the Atlantic and Mediterranean basins, invading the Seine around 2000 (Marescaux et al. 2010). On the Iberian Peninsula, it now occurs in 10 rivers systems in Spain and Portugal, on the Bay of Biscay, Atlantic, and Mediterranean coasts (Araujo et al. 1993; Pérez-Quintero 2008; Oscoz et al. 2009). In 1998, it was found in brackish coastal lakes (the Norfolk Broads) in eastern England (Howlett and Baker 1999) and in 2004 was found in the tidal river Thames (Elliott and zu Ermgassen 2008). In 2010, populations were discovered in tidal freshwater portions of the rivers Barrow and Nore, on the east coast of Ireland (Caffrey et al. 2011).

To a greater extent than in the Americas, an understanding of the invasion in Europe is complicated by the involvement of multiple genetic lineages. While the lineage R (related to or identical with the American A, and Japanese C. leana) is most widespread, it occurs sympatrically with lineage S (morphologically similar to Middle Eastern C. fluminalis, and genetically related to South American lineage C) in the Rhine, Meuse, and Seine rivers. A third lineage, Rlc, from the Rhone River, France, is related to the American lineage B and Chinese and Korean C. fluminea (Pigneur et al. 2011). These occurrences imply multiple introductions. The rapid spread of these clams in Europe has likely been aided by Europe's extensive canal system, as well as many other human vectors.